amalgamation property

A class of L-structuresS has the amalgamation property if and only if
whenever A,B1,B2∈S and fi:A→Bi are elementary embeddings
for i∈{1,2} then there is some C∈S and some elementary embeddings
gi:Bi→C for i∈{1,2} so that g1⁢(f1⁢(x))=g2⁢(f2⁢(x))
for all x∈A. That is, the following diagram commutes.